One example of a known writing implement of the above type is disclosed in Japanese Patent Examined Publication No. 54-14524/1979. According to the teaching of this publication, the device has a tip pipe whose tip portion projects from a forward end of a body to protect a writing lead and a content including an inside ferrule containing therein a lead retainer, a chuck and a fastening device, a fastening device retainer disposed on the inside ferrule, a lead case connected to the chuck, etc. The tip pipe and the content are capable of back and forth movements within the body. A rear end of the fastening device retainer is retained by a mechanism such that the retainer is locked in an advanced position by a first knocking operation and in a retracted position by a second knocking operation. A first spring is interposed between the body and the lead case, and a second spring is interposed between the body and the fastening device retainer. With this construction, a mechanical pencil having a content advancement/retraction mechanism is characterized in that the content is locked in the advanced position by a first large knocking operation, then the writing lead is advanced by a small knocking operation, and the content is locked in the retracted position (or received in place) by a second large knocking operation. In other words, according to the conventional construction mentioned above, the content can be exposed or withdrawn (by a large knocking operation) and the writing lead can be advanced (by a small knocking operation) by properly selecting the modes of the knocking operations.
However, in the above conventional technique, it is required for the user to determine a pressing amount of a knock cap either by guessing or by watching a stepped portion of the knock cap when one of the knocking modes (i.e., a large knocking operation and a small knocking operation) is to be selected.
Obviously, it is difficult for the user to determine the pressing amount of the knock cap by guessing. It sometimes happens that a large knocking operation is made by mistake while a small knocking operation (writing lead advancement operation) is intended. The result is that the content is withdrawn, thus giving an unpleasant feel to the user unable to write. Furthermore, a pressing amount determination operation by watching the stepped portion is convenient because it requires causes the user to watch the knock cap sideways each time the knocking operation is required.